VARIATION IN NATAL DISPERSAL AND PRE-BREEDING MOVEMENT ECOLOGY OF THE COOPERATIVELY BREEDING FLORIDA SCRUB-JAY, APHELOCOMA COERULESCENS

Abstract

Natal dispersal is a crucial life-history event which, at the individual level, represents an opportunity to move to high-quality breeding space associated with increased survival and reproductive success, and at the population level, underlies species distribution, population persistence, and gene flow. Despite its importance, dispersal is often treated as a random process owing to difficulties in monitoring movements of wild animals. Variation in dispersal is primarily driven by the balance between its costs and benefits, with benefits needing to outweigh costs of energetics, exposure to predators and competitors, and finding mates. This tradeoff is pronounced in cooperatively breeding species, in which offspring often delay dispersing from the natal territory. To investigate this complex behavior, I studied variation in natal dispersal and its components in an intensively studied population of Florida scrub-jays (Aphelocoma coerulescens), a cooperatively breeding species that specializes in a rare, fire-maintained oak scrub habitat endemic to Florida. By combining over 35 years of historical data and 5 years of field-collected data, I aimed to understand the drivers and consequences of natal dispersal in this population. I first summarized available data on dispersal patterns in this population, focusing on social and environmental factors related to variation in dispersal timing and distance. I then examined a previously overlooked pattern of dispersal called “staging” in which offspring disperse to join unrelated groups as nonbreeders. This behavioral variation explained some of the patterns previously uncovered, and exposed some proximate and ultimate drivers of dispersal. Next, using field methods along with laboratory work, I studied the physiological costs of prospecting, or information-gathering movements that precede dispersal. I found that prospecting results in oxidative damage, which is also regulated by early-life morphology and condition. Last, I quantified pre-breeding movements using newly developed tracking technology to understand how Florida scrub-jays explore their surroundings prior to dispersal. Combined, my chapters describe intraspecific movement and dispersal patterns, as well as some of their fitness consequences. Ultimately, my study of dispersal variation sheds new light on the complex nature of pre-breeding movement in a cooperatively breeding bird species, and contributes to the growing body of field and theoretical studies of this important life-history stage.